Why is My Aquarium Heater Not Working?

Why is My Aquarium Heater Not Working?

If your aquarium heater is not working you should find the main cause of this problem. In this article, we have added 7 main causes of faulty aquarium heaters and proven methods to repair and fix them.

Why is My Aquarium Heater Not Working? Your aquarium heater is not working it can be because of the broken heaters, faulty internal thermostats, deposition of salts on heater parts, and frequent water change.

Why is My Aquarium Heater Not Working?

An aquarium heater is an electrical component to heat the aquarium water. Most tropical fish can not survive in cold water and require a steady temperature level. Heaters keep the water temperature at a stable level. Tropical fish need 78 to 80 Fahrenheit to live in the aquarium.

Electric heaters convert the electric energy into heat. It contains a resistor heating coil and fan in some cases. When we turn it on, the current passes through heating coils, it gets hot and passes the heat to the surrounding.

The resistor then warms up the surrounding water in the aquarium. The water circulation and fan inside heaters keep the aquarium temperature high. There are different types of aquarium heaters like 

  • hanging out heaters 
  • submersible heaters
  • cable heaters

Choose a submersible heater that can quickly heat the surrounding. The heater size depends upon the location of the aquarium size of tanks and the quantity of water. For efficient heating, we require 2 to 5 watts per gallon. Keep the heater in front of water flow to equally distribute the heat.

Broken aquarium heater

The fish tank heaters are made of glass and have a life span of 4 to 5 years. Sometimes when we use it for a prolonged time, the heater can get broken. Mishandling while transferring it from one tank to another tank is another reason for breakage.

You can check it with your hands to see the breakage of heater components. Unplug the heater and let it cool for 10 to 15 minutes and remove it from the fish tank. Various heaters have lights that warm up the water and, its glass is very fragile. It breaks when we overstock the tank with fish and other objects.

Entertaining the fish with tough toys can also break the heater glass and light. To confirm it’s working, you can also use a thermometer and Insert it in the aquarium to note the temperature. High current flow can break the heater coils and other parts.

You can also add a heater guard around it to keep away all the fish and hard objects from it. You can easily remove the sheet at any time and replace it with a new guard sheet. The fish can get injured when they get close to electric appliances.

Fix it:

Try not to fix a broken heater at home and always consult any repairer for repairing or, better to buy a new heater. Follow the instruction guide before installing it in the fish tank.

Read the complete manual to get information about the terms and conditions of usage. Try to use a multi-way socket to fix the breakage due to high power. Unplug the heater when you change the water in the tank and transfer it to another tank.

Fault in the internal thermostat of aquarium heater

A thermostat is a device in the heater to preset the temperature. It automatically adjusts the heat, give it a command on temperature ranges. When the temperature rises above the preset range heater turn off in below condition, it turns on in the tank.

When the internal thermostat is faulty, the aquarium heater stops working. Sometimes we unintentionally set it to the cold mode and, the water remains cold. Miswiring the thermostat also causes malfunctioning in heaters.


You should also pull out the aquarium heater and check the wiring of the thermostat. There are many alternates of the internal thermostat. The cheapest solution is using a separate thermometer in the tank. Insert it in tanks and regularly check the water temperature.

The LCD screen is more efficient than a thermostat that contains a display screen to show the temperature range and use different lights to indicate the temperature range. Red light means water is too hot, and green means temperature is within range. The blue light indicates the temperature is below.

Dual temperature sensors give a more accurate reading of temperature. A manually adjustable temperature device gives you a chance to adjust the temperature by yourself. You can use temperature dials to add or subtract the temperature reading.

Fault in heating coils

The heating coil is a component of heaters. It is usually made of steel and usually has 2 to 3 heating coils in a glass shield. After prolonged use, it becomes corrode and reduces their efficiency and stop working. Excessive moisture plant leaves and debris can grow mold inside the heating coils.

Due to corrosion, aquarium heaters can overheat the tank also. Fish become stressed in extreme temperatures and become prone to getting many infections. Insulate the coils properly to protect them from water. 

Replacing heating coils with a new one is the best solution. You can replace it at home by measuring the size and thickness of previous heating coils.

Try to buy nichrome heating coils that consist of nickel and chromium and have a high resistance to high temperature and oxidation. It can tolerate up to 1200 Fahrenheit of temperature. You can easily purchase it from the market. First, remove the old coils and place new coils, and fix them in place.

Deposits of salts creeps and minerals

 Fully submersible heaters are waterproof others have a specific water line above which they can easily reside inside water. When we put heaters inside water, salts start to deposit on their parts. They can clog the air filters in it. Salt creep is a thick layer of minerals and salts in the aquarium.

Removing salt creep is difficult. It can not easily wash out with water. You should use any detergent to clean it by making a soapy solution of any detergent. Get a sponge and dip it in water and slowly rub it on the affected areas.

You can use a vacuum or small brushes to wipe out all the deposits on the air filters. Maintain a regular cleaning schedule of the aquarium. It will prevent the unnecessary accumulation of waste around the heater.

Faulty sockets and power supply

In some cases, the heater is not faulty, but the socket supplying power is damaged. You should check the power supply by connecting another device to it.

If it turns on other devices, then the power supply is continuous. You can use a tester to check the power supply of switches. In case it is dysfunctional, replace it with a power switch.

Sometimes the power supply can damage the electric wires of the heater. In such a situation, carefully inspect the wire for any damaged part. When it is faulty, replace the electric cables of the heater.

Short cycles of aquarium heater

The heater cycle consists of turning on and turning off after some time. It is automatic and adjusts the heat accordingly but in some situations, it becomes too short.

The heater quickly turns on and off and causes an unequal distribution of heat. Cycles become short due to overheating and switch off and on immediately. Glass heaters are not heatproof and can not bear high-temperature ranges.

To prevent it check the thermostat and coils of the heater. Place the heater away from the lighting system of the heater. The lighting system makes the coil warm quickly. Using an auxiliary fan can also fix the issue.

Frequent water temperature changes

Frequent changes of water in the tank can also create issues in aquarium heater performance. The temperature of the water should be equal to room temperature.

Keeping it in a cool place makes a temperature difference. When we place the submersible heater in such an aquarium, it can stop working. 

You should check the temperature of the water before keeping it in the heater. Remove the heater from the tank when you are adding water to it.

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